Arm Muscles Anatomy

The main muscles of the arm are:

Biceps Brachii

The biceps brachii, or biceps, is a large, thick muscle on the front of the upper arm between the shoulder and elbow.

• Origin: The biceps brachii has two heads:
  • Long head: Originates from the supraglenoid tubercle of the scapula.
  • Short head: Originates from the coracoid process of the scapula.
• Insertion: Both heads insert on the radial tuberosity and the bicipital aponeurosis into the deep fascia on the medial part of the forearm.
• Function: Flexes the elbow and supinates the forearm. It also assists in shoulder flexion due to its origin from the scapula.
• Innervation: Musculocutaneous nerve (C5-C7).

Brachialis

The brachialis is a muscle in the upper arm that flexes the elbow, allowing the forearm to move closer to the body.  It’s located in the anteroinferior area of the arm, deeper than the biceps brachii, and is part of the floor of the elbow pit.

• Origin: Distal half of the anterior surface of the humerus.
• Insertion: Coronoid process and the tuberosity of the ulna.
• Function: Major flexor of the elbow, particularly when the forearm is in a pronated position.
• Innervation: Musculocutaneous nerve (C5-C7) and, occasionally, contributions from the radial nerve (C5-C7).

Coracobrachialis

The coracobrachialis is a slender muscle in the upper arm’s front compartment that flexes and adducts the shoulder joint’s glenohumeral joint. It also helps rotate the arm internally and stabilizes the humeral head.

• Origin: Coracoid process of the scapula.
• Insertion: Medial surface of the humerus shaft.
• Function: Flexes and adducts the shoulder joint. It also stabilizes the humerus within the shoulder joint.
• Innervation: Musculocutaneous nerve (C5-C7).

Triceps Brachii

The triceps brachii, or triceps, is a large, thick muscle on the back of the upper arm that’s responsible for straightening the arm. The triceps is the only muscle that runs along the humerus, the main bone of the upper arm, between the shoulder and elbow.

• Origin: The triceps brachii has three heads:
  • Long head: Originates from the infraglenoid tubercle of the scapula.
  • Lateral head: Originates from the posterior surface of the humerus, superior to the radial groove.
  • Medial head: Originates from the posterior surface of the humerus, inferior to the radial groove.
• Insertion: All three heads converge into a single tendon that inserts on the olecranon process of the ulna.
• Function: It extends the elbow and the long head also assists in shoulder extension and adduction.
• Innervation: Radial nerve (C6-C8).

Other important muscles of the arm are:

• Deltoid: The deltoid covers the shoulder joint and helps in the abduction, flexion, and extension of the arm.
• Brachioradialis: Located on the lateral side of the forearm, the brachioradialis assists in flexing the elbow joint, particularly when the forearm is in a mid-position.
• Flexor Carpi Radialis: Located on the anterior side of the forearm.
• Flexor Carpi Ulnaris: Situated on the posterior side of the forearm.
• Extensor Carpi Radialis Longus and Brevis: These muscles, located on the posterior side of the forearm, extend and abduct the wrist.
• Extensor Carpi Ulnaris: Also situated on the posterior side of the forearm, this muscle extends and adducts the wrist.

Also Read: Difference between Origin and Insertion Muscles

The arm body part is the upper limb of vertebrates. Anatomy of the arm involves the detailed study of its bones, muscles, nerves, blood vessels, and connective tissues. Learning about the arm muscles and arm bones helps in understanding how movements are coordinated and how injuries can be prevented or treated.

In this article, we will cover the anatomy of the arm and read about the nerve supply and blood supply in the arm along with arm muscles and bones, in detail.